OLEDs have been the subject of a considerable amount of research in recent years because of their use and potential use in a wide variety of electroluminescent devices. For instance, a single OLED can be used in a discrete light emitting device or an array of OLEDs can be used in lighting applications or flat-panel display applications (e.g., OLED displays). OLED displays are known to be very bright and to have a good color contrast and wide viewing angle. However, OLED displays and in particular the electrodes and organic layers located therein are susceptible to degradation resulting from interaction with oxygen and moisture which leak into the OLED display from the ambient environment. It is well known that the life of the OLED display can be significantly increased if the electrodes and organic layers located therein are hermetically sealed from the ambient environment. Unfortunately, it has been difficult to develop a sealing process to hermetically seal the OLED display. Some of the factors that can make it difficult for one to properly seal the OLED display are briefly mentioned below:                The hermetic seal should provide a barrier for oxygen (10−3 cc/m2/day) and water (10−6 g/m2/day).        The size of the hermetic seal should be minimal (e.g., <2 mm) so it does not have an adverse effect on size of the OLED display.        The temperature generated during the sealing process should not damage the materials (e.g., electrodes and organic layers) within the OLED display. For instance, the first pixels of OLEDs which are located about 1-2 mm from the seal in the OLED display should not be heated to more than 100° C. during the sealing process.        The gases released during sealing process should not contaminate the materials within the OLED display.        The hermetic seal should enable electrical connections (e.g., thin-film chromium electrodes) to enter the OLED display.        
Today one way to seal the OLED display is to form a hermetic seal by heating and softening a frit that is doped with a material which is highly absorbent at a specific wavelength of light. In particular, a high power laser is used to heat-up and soften the frit to form a hermetic seal between a first substrate plate (cover glass) which has the frit located thereon and a second substrate plate (substrate glass) which has the OLEDs located thereon. The frit is typically ˜1 mm wide and ˜6-100 um thick. If the absorption and thickness of the frit is uniform, then the sealing can be done at a constant laser energy and a constant speed which causes a uniform temperature rise within the frit. However, when the frit is relatively thin, then 100% of the laser energy is not absorbed by the frit and instead some of the laser energy is absorbed or reflected by metal electrodes which cross the frit at certain points and are attached to the OLEDs. Since, it is often desirable to use thin frits and the metal electrodes often have different reflectivity and absorption properties as well as different thermal conductivities than the bare substrate glass, this can create an uneven temperature distribution within the frit during the sealing process. The uneven temperature distribution within the frit can lead to problematical cracks, residual stress and/or delamination which prevents/degrades a hermetic connection between the cover glass and the substrate glass.
To address this sealing problem, the assignee of the present invention has developed several different sealing techniques which have been disclosed in U.S. patent application Ser. No. 11/095,144 filed on Mar. 30, 2005 and entitled “Method for Backside Sealing Organic Light Emitting Diode (OLED) Displays” (the contents of this document are incorporated herein by reference). Although these sealing techniques work well there is still a desire to develop new and improved sealing techniques which can be used to hermetically seal an OLED display (or glass package). This particular need and other needs have been satisfied by the sealing device and the sealing method of the present invention.